1. Field of the Invention
This invention lies in the field of sonic logging systems for boreholes. More particularly, it is concerned with the logging of deep boreholes in the earth. Still more particularly, it concerns the use of a sonic transducer which transmit a beam of high frequency acoustic energy into the borehole wall directed in a radial plane, and receives the returned reflected acoustical energy signal from a reflecting surface, such as the wall of the borehole, and transmits a processed electrical scan signal derived from such received signal, to the surface of the earth, through the cable which supports the instrument, or sonde, for further processing.
Still more particularly, it concerns improvements in such logging devices, and in particular, the use of two or more transducer systems on a single rotating assembly so that multiple probing signals are sent outwardly from the axis of the borehole and multiple reflected sonic signals are received, converted to electrical scan signals, which are then utilized in various ways.
Still more particularly, this invention concerns improvements in methods and apparatus for processing multiple simultaneous analog electrical scan signals (ESS) in the sonde for transmission to the surface in real time, over conventional logging cables which may have only a single, or possibly only two conventional intermediate frequency signal transmission channels.
Still more particularly, this invention concerns improvements in such logging devices whereby with multiple transducers, the logging sonde can be traversed at higher speed without losing any detail of the sonic log.
2. Description of the Prior Art
This field of science and engineering is not new. It has been in useful operation in the logging of boreholes in the earth, such as oil and gas wells, for a number of years. There are various patents issued on selected features of these systems, and including the basic system, which form no part of this invention.
Examples of the prior art are illustrated by U.S. Pat. No. 3,369,626, entitled: "METHOD OF AND APPARATUS FOR PRODUCING A VISUAL RECORD OF PHYSICAL CONDITIONS OF MATERIALS TRAVERSED BY A BOREHOLE", issued Feb. 20, 1968 in the name of J. Zemanek, Jr. There is also U.S. Pat. No. 3,668,619, entitled: "THREE-DIMENSIONAL PRESENTATION OF BOREHOLE LOGGING DATA", patented June 6, 1972 in the name of Charles L. Dennis; U.S. Pat. No. 3,550,075, entitled: "SYSTEM FOR DISPLAYING TIME INFORMATION IN ACOUSTIC WELL LOGGING SYSTEM", issued Dec. 22, 1970 in the name of D. W. Hilchie et al; and U.S. Pat. No. 3,836,953, entitled: "ACOUSTIC CALIPER LOGGING", issued Sept. 17, 1974 in the name of Jerald C. Summers. There is also additional art recorded in the form of other patents, and in technical papers presented at technical society meetings, so that further description or statement of the art is not necessary at this time.